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The femoral posterior condylar offset (PCO) has been viewed with increased significance for knee joint movement patterns and has been discussed for its possible implication for femoral component rotation in total knee arthroplasty (TKA). However, a great inter-individual variability in medial and lateral PCO size has also been demonstrated. Though the medial and lateral PCO seem closely related to the functional flexion axis (fFA), determined by the radius curvature of the medial and lateral femoral condyle, the relationship of both parameters considering their impact on the accuracy of established reference axes for determining femoral component rotation in TKA remains unknown. The objective of this paper was, therefore, to compare the individual fFA with the anatomical and surgical transepicondylar axis (aTEA; sTEA) and with the posterior condylar axis (PCA) considering the medial and lateral PCO size. It was hypothesized that the disparity of the PCO influences the accuracy of the sTEA, aTEA, and PCA for determination of femoral component rotation in TKA. MRI investigations of 56 consecutive non-arthritic knee joints (male/female 28/28; mean age 22.8 years; range 16-59 years) were used for this study. Coronal, sagittal and transverse MRI images were used to measure the medial and lateral PCO and to determine the fFA, aTEA, sTEA, and PCA for each subject as described previously. A paired two-tailed t-test was used to test for differences between the medial and lateral PCO sizes. Deviation of the aTEA, sTEA and PCA from the fFA were analyzed with a one-sample t-test. Correlation analysis (Pearson r) was used to determine the relationship between the PCO ratio (medial-to-lateral PCO) and the deviation of the aTEA, sTEA and PCA from the fFA in each subject. The level of significance was set at 0.05. The mean medial PCO was 34.0 mm (90%CI 28.72-30.55 mm; range 26.3 to 44.7 mm) and the lateral PCO averaged 29.64 mm (90%CI 30.3-31.4 mm; range 14.3 to 39.1 mm) (p Differences of the medial and lateral PCO size are a common finding. The PCA had the best match with the fFA, regardless of medial-to-lateral PCO disparity. Only the sTEA was influenced to a small extent by variation of the PCO-ratio.

Purpose The geometry of the tibial plateau and its influence on the biomechanics of the tibiofemoral joint has gained increased significance. However, no quantitative data are available regarding the inclination of the medial and lateral tibial slope in patients with patellar instability. It was therefore the purpose of this study to evaluate tibial slope characteristics in patients with patellar dislocations and to assess the biomechanical effect of medial-to-lateral tibial slope asymmetry on lateral patellar instability. Methods Medial and lateral tibial slope was measured on knee magnetic resonance images in 107 patients and in 83 controls. The medial-to-lateral tibial slope asymmetry was assessed as the intra-individual difference between the medial and lateral tibial plateau inclination considering severity of trochlear dysplasia. The effect of tibial slope asymmetry on femoral rotation was calculated by means of radian measure. Results Severity of trochlear dysplasia was significantly associated with an asymmetric inclination of the tibial plateau. Whereas the medial tibial slope showed identical values between controls and study patients (n.s.), lateral tibial plateau inclination becomes flatter with increasing severity of trochlear dysplasia (p

The purpose of this study was to analyze the impact of monopolar radiofrequency energy treatment on subchondral bone viability. The femoral grooves of six chinchilla bastard rabbits were exposed bilaterally to monopolar radiofrequency energy for 2, 4 and 8 s, creating a total of 36 defects. An intravital fluorescence bone-labeling technique characterized the process of subchondral bone mineralization within the 3 months following exposure to radiofrequency energy and was analyzed by widefield epifluorescence optical sectioning microscopy using an ApoTome. After 2 s of radiofrequency energy exposure, regular fluorescence staining of the subchondral bone was evident in all samples when compared to untreated areas. The depth of osteonecrosis after 4 and 8 s of radiofrequency energy treatment averaged 126 and 942 µm at 22 days (P

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months. peerReviewed

Introduction: To reduce complications, a minimally invasive technique for the treatment of dislocated intraarticular fractures of the calcaneus was used. Therefore previously described closed reduction and internal fixation techniques were combined and modified. Materials and methods: Sixty-seven out of 92 calcaneal fractures could be retrospectively evaluated with an average follow-up time of 5.7 years (minimum 210 years follow-up). For radiographic evaluation, plain radiographs and CT scans were obtained. The Zwipp score was used for clinical evaluation. Sanders type II, III and IV fractures were diagnosed. Results: Length of surgery averaged 61 min (range 20175 min). The incidence of subtalar arthritis was correlated to the severity of fracture. Böhler’s angle was restored in 70.1% (47 of 67) of the cases. On the last follow-up evaluation the average Zwipp score was 130 points (range 48186 points). The majority (77.7%) of patients were content with their treatment result. The rate of significant complications was 6.5%. Discussion: Compared to open techniques the presented minimally invasive technique showed comparable results with a low rate of serious complications and is a viable alternative for the treatment of intraarticular, dislocated calcaneal fractures. peerReviewed

The medial and lateral tibia plateau geometry has been linked with the severity of trochlear dysplasia. The aim of the present study was to evaluate the tibial slope and the femoral posterior condylar offset in a cohort of consecutive subjects with a trochlear dysplastic femur to investigate whether the condylar offset correlates with, and thus potentially compensates for, tibial slope asymmetry. Magnetic resonance imaging was used to assess the severity of trochlear dysplasia as well as the tibial slope and posterior offset of the femoral condyles separately for the medial and lateral compartment of the knee joint in 98 subjects with a trochlear dysplastic femur and 88 control subjects. A significant positive correlation was found for the medial tibial slope and the medial posterior condylar offset in the study group (r(2) = 0.1566; P < 0.001). This relationship was significant for all subtypes of trochlear dysplasia and was most pronounced in the severe trochlear dysplastic femur (Dejour type D) (r(2) = 0.3734; P = 0.04). No correlation was found for the lateral condylar offset and the lateral tibial slope in the study group or for the condylar offset and the tibial slope on both sides in the control group. The positive correlation between the medial femoral condylar offset and the medial tibial slope, that is, a greater degree of the medial tibial slope indicated a larger offset of the medial femoral condyle, appears to represent a general anthropomorphic characteristic of distal femur geometry in patients with a trochlear dysplastic femur.

Purpose The aim of this study was to evaluate the clinical outcome and differences in anterior–posterior laxity of ACL reconstruction using a bioabsorbable interference screw for femoral graft fixation when compared to femoral bioabsorbable cross pin fixation. Methods Clinical outcome was evaluated among 59 patients 1 year after arthroscopic ACL reconstruction with hamstrings graft in a prospective, non-randomised study. In 31 cases, femoral fixation of the graft was performed using a bioabsorbable interference screw. In 28 cases, two bioabsorbable cross pins were used for femoral fixation. Patients were evaluated using Tegner, Lysholm and Marshall scores, the visual analogue scale for pain and KT-1000 arthrometer measurement. Results No significant difference (P ≥ 0.05) was observed at follow-up for the knee scores. The average Tegner score was 5.83 points (±2.00) for the interference screw fixation and 5.83 points (±1.24) for the cross pin fixation; the average Lysholm score was 93.58 (±5.79) to 92.72 (±6.34) points; and the average Marshall score 46.72 (±2.4) to 47.30 (±2.35) points. No significant difference was found for the visual analogue scale for pain. KT-1000 arthrometer measurement revealed a significant (P

Firstly, the way of implementing approximatively the initial rollback of the natural tibiofemoral joint (TFJ) in a total knee replacement (AEQUOS G1 TKR) is discussed. By configuration of the curvatures of the medial and lateral articulating surfaces a cam gear mechanism with positive drive can be installed, which works under force closure of the femoral and tibial surfaces. Briefly the geometric design features in flexion/extension are described and construction-conditioned kinematical and functional properties that arise are discussed. Due to a positive drive of the cam gear under the force closure during the stance phase of gait the articulating surfaces predominantly roll. As a result of rolling, a sliding friction is avoided, thus the resistance to motion is reduced during the stance phase. Secondly, in vivo fluoroscopic measurements of the patella tendon angle during flexion/extension are presented. The patella tendon angle/ knee flexion angle characteristic and the kinematic profile in trend were similar to those observed in the native knee during gait (0°-60°).

Purpose The purpose of this study was to investigate whether the femoral part of the medial patellofemoral ligament (MPFL) and its injury can be accurately assessed by standard knee arthroscopy in first-time patellar dislocations or whether preoperative MRI is required to determine injury location in patients where primary MPFL repair is attempted. Methods Twelve patients with acute first-time dislocations and MRI-based injury of the femoral MPFL and ten patients with recurrent patellar dislocations underwent knee arthroscopy with the use of a 30-degree optic and standard antero-medial and antero-lateral portals. The femoral origin was marked with a cannula under lateral fluoroscopy. Arthroscopic findings of the location of the native femoral MPFL and its injury were compared to the results of MRI and mini-open exploration. Results In acute cases, the average time from primary patellar dislocation to MRI evaluation was 3 days (1–9 days), and the average time from MRI to surgery was 8 days (3–20 days). The native femoral origin of the MPFL was not visible in any of the chronic cases during arthroscopy. In addition, in all acute cases, arthroscopy failed to directly visualize injury of the femoral MPFL (0 of 12), but mini-open exploration confirmed injury in 11 of 12 patients. This means that arthroscopy was less accurate than MRI for the diagnosis of femoral MPFL injury (P

Periprosthetic osteolysis is a well recognized complication of total hip arthroplasty that leads to implant failure. The ability to accurately assess and visualize the position and volume of periacetabular bone defects is paramount for clinical observation and medical treatment, as well as pre-operative planning of revision surgery. We have developed a modified magnetic resonance imaging (MRI) protocol that is useful in detection and quantification of periacetabular bone loss. The purpose of this study is to compare MRI to plain film analysis in the assessment of periacetabular bone loss using a cadaver model. MRI was 95% sensitive in the detection of lesions. Specificity was 98%, and accuracy was 96%. Lesion detection was not statistically dependent on lesion location (p=0.27). The mean absolute error in determining lesion size was 0.8+/-2.2 cm3. There was a correlation between increasing lesion size and lesion detection (p=0.02, logistic regression). The largest lesion that was missed by MRI analysis measured 2.8 cm3, and all lesions 3.0 cm3 were correctly identified, with a relative error volume measurement of 12.4+/-25.3%. This correlated to an absolute error of 1.4+/-2.4 cm3. Using conventional radiographic analysis, the overall sensitivity of lesion detection was 52%, and the specificity was 96%. Using plain film analysis, identification of true lesions depended on the location with 83% of ilial lesions, 64% of pubic lesions, 55% of ischial lesions, and 0% of posterior wall lesions correctly identified. The modified MRI technique utilized did allow for accurate visualization of simulated osteolytic lesions, and may provide a suitable noninvasive method to provide serial assessment of clinical periacetabular osteolysis without the use of ionizing radiation.